


Sleeping With The Fishes

by antigrav_vector



Category: Captain America (Movies), Iron Man (Movies), Marvel, Marvel (Movies), Marvel Cinematic Universe, The Avengers (Marvel Movies)
Genre: Alternate Universe, Alternate Universe - Canon Divergence, Alternate Universe - Fantasy, Avengers: Age of Ultron (Movie) Compliant, Avengers: Age of Ultron (Movie) Spoilers, First Kiss, Flirting, Get together fic, Howard Stark's A+ Parenting, Implied Sexual Content, M/M, Mer!AU, No actual porn, Oblivious!Tony, Post-Avengers: Age of Ultron (Movie), Steve knows what he wants and how to get it, but not for long, goes AU just at the end of Age of Ultron, implied sex, merman!Tony, pov fic
Language: English
Status: Completed
Published: 2015-07-28
Updated: 2015-07-28
Packaged: 2018-04-11 17:21:26
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,503
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4445132
Author URL: https://archiveofourown.org/users/antigrav_vector/pseuds/antigrav_vector
Summary: <blockquote class="userstuff">
              <p>Steve is human, albeit not baseline. Tony is merfolk. And when they finally get their acts together and <i>talk</i> rather than arguing some more, well, a different kind of sparks start flying.</p>
            </blockquote>





	Sleeping With The Fishes

**Author's Note:**

  * For [spookyrumba](https://archiveofourown.org/users/spookyrumba/gifts), [ssyn3](https://archiveofourown.org/users/ssyn3/gifts).



> With thanks to my lovely beta reader, lil_1337, who gave me the title for this, in addition to helping me wrangle the grammar.
> 
> This here is intended as giftfic for my two lovely Big Bang artists, [ssyn3](http://archiveofourown.org/users/ssyn3) and [Popcornzoe](http://archiveofourown.org/users/Popcornzoe). Call it a thank you for their continued awesomeness.

Tony's current problem was twofold.

Firstly. They'd only just started recovering from Ultron's attack, and the team had shattered. Bruce had disappeared to god only knew where without a word, probably tormented by the destruction he'd caused in Wakanda at Wanda's provocation. Natasha had decided to stay on, but Clint had gone back home to his family. He felt they needed the protection, now that they'd burned that address by using it as a safehouse and potentially drawing attention to the location. He himself wasn't sure whether he'd return. Tony was betting he would eventually get bored, though, and come back to New York. Sam and (surprisingly enough) Wanda were also staying on. Rhodey had pled prior obligations before the Air Force had appeared to hustle him off to debrief. He had no idea where Thor had gone. Probably off to see Jane, or visit home. And Steve, as their captain, was leading the remnants of the team, and training them to work together, safely outside the city, somewhere upstate.

Which left Tony to return to his once-more ruined penthouse to repair the suit and use the short period of time he had to prepare himself to field questions from the press and the various governments about the whole mess. Which had been mostly his fault. Awkward.

But he'd defended himself against similar accusations more times than he could count, while he'd been building weapons. People were always ready to blame the messenger -- or, in this case, the supplier -- when things went wrong. They'd done exactly that in the early 90s right after he'd taken over the reins of the company and been contracted to design a variety of weapons that were later used in the Persian Gulf War[1]. They'd been used incorrectly and people had gotten killed that shouldn't have. And that had somehow been Tony's fault.

Anyway. Yes, he felt guilty as fuck over the whole mess. But he'd already personally paid for it all in spades, played an instrumental role in also _stopping_ the propagation of the disaster, and was funding basically all of the clean up efforts in one way or another, so the haters could go fuck themselves. He'd defend his team and his company, but more than that was beyond him at this point. His lawyers and PR experts would be getting briefed to handle the rest as soon as he and Pepper had managed to come up with an official stance for the company. They were getting well-paid to deal with this kind of crap.

And secondly, Steve had started pushing him for an answer. Cap had floored him after the final battle in Sokovia and their flight back to SHIELD's new headquarters outside the City with an invitation to dinner as he'd walked Tony out to his car. A _private_ dinner. Tony had given him a wishy-washy quip in reply about checking his calendar before driving off, assuming that would be the end of it. There was no way that had been a serious offer, right?

He'd had to get back to the Tower to start putting out political fires, and that had been in the forefront of his mind. The idea of dinner had been brushed off pretty quickly, really. And in retrospect, he probably should have known better.

That had only gained him a week, which he'd wasted not thinking about Steve's offer. When he'd resurfaced from the haze of Senate hearings and TV appearances -- all of which had blurred together, seeing as everyone was throwing the same accusations around -- he discovered that he had ten missed calls from Steve and three messages. He deleted those without opening them. If it was something important, Steve would call back.

Steve's next call had come in a few hours later, as Tony was working on repairing the suit and simultaneously considering a new set of upgrades for the armour. Nothing immediately viable, really, but an interesting what-if kind of design. The--

"Tony, are you even listening to me?"

"Yeah, sure. Wanda's having fun training with Natasha, and Pietro's finally recovering a little. Gotcha. I can do repairs and listen at the same time, Cap, and you know that."

"That's not what I said," Steve sounded amused, so Tony stopped actively listening. He needed to focus to fix the connection on this circuit board and actuator pair. Steve was still talking when he tuned back in twenty-five seconds later.

"-- on Friday evening?"

"Yeah, sure, why not," he agreed absently. That transistor line was looking mangled. Shit. How had he missed that.

"Good. See you Friday, Tony," Steve replied, then the line clicked off.

"Wait, what," he asked the empty room.

"I think you just agreed to a date, Mr. Stark," FRIDAY replied, and he was jerked out of his confusion.

It was still jarring not to hear JARVIS' smooth tones answer him. It really was a bit messed up, but he missed the sass and the snark. JARVIS had been a part of his life for, fuck, almost two decades, in various iterations. FRIDAY was good, but she was no JARVIS. Didn't know him inside and out like JARVIS had. Hadn't gotten all his preferences dialed in down to the micron. Wasn't as refined in her handling of the suit, when he flew. In a lot of ways it was like mourning a friend, he supposed, but JARVIS wasn't dead. He was transmuted, and had a body now. He was going to be part of Steve's new team, once they worked out what his capabilities were and how he fit into the mix. And yet...

"What," he eventually managed to ask again, once the ball of choking emotions had calmed a little.

Rather than reply verbally, FRIDAY obligingly played back the last few sentences of the call, and, damn. He had.

Shit. That was Steve's inner tactician taking advantage of his inattention. The man was probably going to blithely show up on Friday, whether Tony wanted it or not, and drag him out of the Tower bodily, if necessary.

Tony let his head fall to the table with a groan, scattering components and knocking over his soldering iron. He ignored the mess.

Even if Steve was -- impossibly -- interested in a relationship, Tony highly doubted he'd stick around once he found out a few things, and it wasn't like he'd done anything to deserve this. Good things fell into his lap sometimes but he never got to keep them. (Pepper was the case in point, here, as his longest lasting romantic relationship, but Rhodey came in a close second, as his best friend, with the way his military obligations kept him overseas for a minimum of nine months of the year. It'd been six already when the Ultron mess went down, and that barely counted as getting to see Rhodey, with the way they'd been all business and only working together for about fifteen minutes.)

More important, though, was the fact that Tony had a fish tail sometimes. He'd pretty much always known about it. Not a new thing. The scales had first appeared when he'd been about five years old, and his father had yelled. That had not been a good day. He hadn't known how to make the scales disappear again, and his mother had been too busy fighting with Howard to help him. That was when he'd learned that he'd inherited the scales from her. Much much later, he'd learned that she'd turned Howard. He was pretty sure that not even Obie had known, despite being so close to the family. That information had been kept incredibly secret, at Howard's behest.

Now, only Rhodey and Pepper knew. Pepper had taken the revelation of his fishy half surprisingly well. She'd walked in on him soaking his scales in the jacuzzi once, and screamed at him about it for fifteen minutes. He was pretty sure it still topped the list of worst things she'd caught him doing, just for the raw shock value.

Rhodey had found out from Pepper a few days later and come by to grill Tony about it.

That was really one of the worst parts of starting a relationship. It had been rough for a few weeks after he'd told Pepper. His other relationships didn't count; they were too short for him to consider telling his partners anything about his secret. But Steve… Steve would not let this go easily. Tony knew that much for sure. Once Steve had his sights set on someone, he didn't give up easily. Case in point, the Winter Soldier. Steve had decided he was getting his friend back, and he wasn't about to let anything get in his way. Up to and including all of HYDRA and three helicarriers. And it was almost certain that Steve would take a similar stance on a romantic relationship. He was still occasionally visiting Agent Carter. Tony had heard about it on his own last visit with her.

He was conflicted about the idea of being pursued by Steve (and, yes, that was apparently a thing that could and did happen and he was still a bit in shock over it) because having unprotected sex with him would turn him. In something of an ironic twist, considering the stories about werewolves and vampires (both of which were pure myth, by the way,) merfolk could increase their numbers either by having children or by finding human mates and turning them. Or both.

In the end, though, after debating with himself for a while, Tony gave in and asked FRIDAY to block in dinner on his calendar and remind him.

It wasn't like he was going to turn down an invitation like that if Steve actually meant it. You'd have to be incredibly asexual or dead not to be interested in a man like him.

The rest of the week passed uneventfully, and all too soon, Tony found himself staring into the depths of his closet, wondering what to wear. He had no idea where Steve intended to go for dinner.

He eventually decided on a middle of the road pair of slacks and a nice button-down. The odds were good that Steve wasn't going to take him anywhere incredibly fancy.

As he was tugging his cuffs into place, FRIDAY notified him of Steve's arrival.

"Send him up, FRIDAY," he replied, securing his plainest cufflinks in place, and turning to walk out into his foyer and wait in front of the elevator doors.

Moments later, it opened, and Steve stepped out.

Deciding that Tony was mostly ready, Steve all but frog marched him out the door, despite Tony's protests and (thankfully successful) attempt to grab for his wallet. Tony had found himself led down to the garage, chivvied into a still obviously brand new helmet and onto Steve's bike (holy fuck, that might be a new turn on), and chauffeured out to some tiny hole in the wall Italian place in Red Hook.

The food was legitimately amazing, and Tony wasn't sure whether he wanted to know how Steve had found this place. It had probably required making deals with at least two mafia bosses. The drive back was another series of surprisingly peaceful moments. Tony spent it pressed up against Steve's back, mostly at Steve's insistence, and that was just...

Tony didn't move from his position until they were back in the Tower's underground lot. When he managed to pry himself away, feeling oddly bereft, Tony managed to scrape together the thought to offer coffee. "You'll want some before you drive off into the night. I know the caffeine does nothing for you, but it'll wake you up anyway."

And that was really a bit more emotion than he'd intended to reveal, but it was out there now, and Steve was nodding. Smiling.

"Sure."

Somehow things snowballed from there until Tony found himself tumbling into bed with Steve, who was very determinedly working Tony's pants off.

The realization hit him like a shock of cold water. He managed to insist on a condom, but that was far as he got before the hormones pulled them both under, and everything became a blur of heat and sensation.

When he came back to himself, Steve was possessively wrapped around him, all muscles and warm bulk, and his watch read 12:24am. It was... weirdly comforting. But it was his reluctance to move that really drove the point home for Tony. He didn't want to lose this. And that (Tony wanted to groan) meant a few very awkward conversations.

It had been fairly easy to get through them with Pepper; she'd found out hands on. Well, kind of. The hands on part had come later. They'd experimented a little. But the point was that explanations had been more or less moot.

Maybe, he decided, that approach would also work on Steve?

The man did adapt ridiculously quickly to just about anything that the universe threw at him, and he seemed genuinely interested, judging by the way he'd doggedly pursued the relationship. And that wasn't even going anywhere near the topic of Steve's steadfast stubbornness. The fact that he'd persisted in trying to get Tony to agree to a date for more than a week in the face of Tony's vague attempts to put him off spoke volumes.

In fact, Tony rolled his eyes, Steve'd not been overly subtle with those overtures of his during their fight with Ultron, either. This pretty clearly wasn't a decision made in the heat of the moment.

Screw it, Tony decided. Sometimes you had to run before you could walk. He was going to go for it. Even if it didn't last, Steve was his teammate, and trustworthy. He wasn't about to go blab to the tabloids, and if he did, Tony would know exactly who to fight things out with. And simply letting someone walk in on him while shifted was, bar none, the best way to get the 'is this a prank' conversation over and done with in a hurry. In any case, if Steve was going to throw a fit or break up with him over his scales, Tony would rather have it happen now, and not a few months in, after he'd gotten attached.

Well. More attached.

It had been so difficult to go back to sleeping alone after his breakup with Pepper. He didn't want to go through that -- or the accompanying moodiness and insomnia -- again if he could avoid it. Stupid hormones had taken weeks to regulate properly, that time. And he still sometimes woke up reaching for her, his subconscious convinced that she would be there.

Right. Bath time. It had been weeks since he'd had a proper soak, anyway, and he was starting to really feel the itch. (Howard had handled that by drinking until he couldn't hold back anymore. He'd also raged about it in the later years. Tony had tried a similar tactic, briefly, as a young teen. It hadn't worked well. His mother had taught him how to deal with it, after that.)

Gingerly, he pried Steve's arm carefully loose and pushed the wandering thoughts aside. Tony could see Steve's eyes slit open, but Steve didn't move except to roll onto his back, watching appreciatively as Tony stretched and grumbled wordlessly before shuffling into the bathroom, still nude and stifling a yawn.

He somewhat pointedly left the door open and started the water running. An obvious invitation to anyone versed in reading people. He was fairly certain the invitation would be accepted.

Pouring a liberal amount of bubble bath into the running water, Tony tested the temperature with his toes. Mmm, yes, that would feel nice. The suds weren't just because he liked them, no matter how 'girly' other people labeled him for it. It was also partly strategic. They would at least let him hide, if the sight freaked Steve out. He wouldn't be able to run, though. Tony winced; that could be a problem. Not a likely one, granted, but still a consideration.

The sheets rustled out in the bedroom, and Tony took that as his cue to slide into the bath. 

Taking a deep breath and holding it for a moment, Tony focused. When the transformation was started voluntarily, it was much less painful, but the feeling of his scales coming up through his skin was still like a full-body itch that scratching wouldn't help. It stung and throbbed with his heartbeat for a few long seconds before it settled. The reshaping of his leg bones to have a few extra joints apiece and the shifting of the muscles and ligaments to adjust for that manifested as a dull ache ending in a sharp snap that always made him hiss, expecting pain but never quite getting it.

Thank the gods that the human myths of merfolk with single fish tails were wrong. Having his skeleton rearrange itself like that every time he shifted would probably be horrendously painful and tiring. He just had scales covering his legs up to his waist, and fins both at the outer sides of his transformed thighs and where his toes would have been[2], and that was exhausting enough. He'd always liked the bright colors he'd been gifted with by nature, though. A deep crimson shading into maroon, his scales were almost the same red as his armour, but somehow managed to be a lot more lustrous and almost iridescent. The fins at his feet and 'thighs' shone a bright gold in the right light, and a darker shade of blood red the rest of the time.

When the shift was forced, as could happen in some cases, such as when you went too long without a soak, it could be... bad. Painful, on a number of levels ranging from the physiological to the psychological. He'd been on the verge of an involuntary shift near the end of his capture in Afghanistan, and only the sheer amount of stress his body had been under had let him avoid it. The moment he'd had a chance to heal and uncoil a little, physically and emotionally, the need had made itself known so sharply that Tony had nearly doubled over.

Shaking off the thoughts, he let the water warm and soothe his scales as he settled into the bath.

Moments later, footsteps alerted him to Steve's approach. When Steve stopped to lean against the doorframe and look at Tony -- who was up to his waist in bubbles and warm water -- like he was memorizing the scene to draw later, Tony suppressed a shiver.

"Room for one more," Steve asked after a moment.

Tony turned to face him properly, draping himself over the edge of the tub and resting his chin on his crossed arms. "That depends."

"On what?" Steve pushed off the doorframe and stalked closer, the movements full of a predatory grace. It was hotter than Tony thought it had any right to be.

He had to swallow to get his voice to work. "This," he replied succinctly and slowly raised one fin out of the water.

Steve stared. "Tony?"

"Yeah?"

"Why do you have fish fins? Do we need to call Dr. Strange?"

Tony blinked. That was distinctly not the reaction he'd half expected. "No, Steve. I'm fine. No random magic here."

"You... What?"

Steve couldn't find full sentences, apparently. Tony huffed an amused breath into his arms. Clearly this talk was going to go differently than it had with Pepper. "Come here, Steve," he patted the edge of the tub, inviting Steve to sit down. "It's a thing. Not many people know this about me, but if you're serious about this... Us... You needed to know."

"Know what, exactly," Steve prompted as he settled on the edge of the tub, gingerly. He looked like he was only a careless comment away from raising the alarm and calling in reinforcements to 'fix' an imagined problem, whether Tony wanted him to, or not.

It was kind of sweet, but utterly unnecessary.

"That every so often I need to soak like this. And that the scales are basically like an STI. You don't want scales of your own, you wear a rubber." He paused and leered at Steve. "Or I do, if that's something you want."

Steve looked a little dazed, but he was obviously recovering quickly from the surprise. "Can I touch--?"

Tony grinned. "If you want, you can even come join me in the bath."

The smirk that tugged at Steve's features was very promising. "You do know that the serum means I can't catch anything, don't you?"

"Pretty sure I know more about the science than you do," Tony retorted. "What dad's notes said was that you fought off anything you caught more quickly than normal. Not that you were magically immune to everything. And this is no ordinary disease. It just acts a lot like one in the way it spreads. I have no idea how the serum would react to it. Might have the opposite effect and make it more permanent."

"What makes you think that would be so horrible," Steve shot back.

Tony stared at him. "You sure about that?"

Steve shrugged. "Well, either I'll get a temporary set of scales and then the serum will take care of it, or I'll get a more permanent ability to dive without a breathing apparatus. Could be useful for missions with underwater components. How deep can you go?"

"I don't know. Never tested the limits." Tony admitted, shifting uncomfortably. "Before Iron Man, I had other priorities. After, well, it took me a while to get to a point where I could duck my head under the surface again. Still not exactly something easy. And you're being very calm about this."

Steve knew Tony's file. Could guess at the reasons and emotions lurking behind his statement. Tony was suddenly grateful about that. Not having to rehash the experience again was a plus. Steve nodded slowly before he responded. "Tony, since I've woken up in the twenty-first century, I've been introduced to," he started ticking off points on his fingers, "the concept of a flying aircraft carrier with near flawless optical camouflage; a man who grows to twelve feet tall and turns green when he gets angry; not just one but _multiple_ highly advanced artificial intelligences; a man who wears a cape, can actually do magic, and calls himself the Sorcerer Supreme; and a billionaire genius who not only rediscovered vibranium but built himself what is essentially a flying tank. My day job is filled with bizarre people and objects, and magic. Why would something like this upset me? Besides. The colors suit you."

The sudden reappearance of the smirk on Steve's face, combined with the way his tone dipped down into something dark and promising made Tony unaccountably edgy. "I--"

"If you'd rather not continue," Steve said, reaching down to trail his fingers along the fin Tony had forgotten he was holding above the water's surface, making him shudder with the sensation, "you'd better tell me now."

The feeling reminded him of that time he'd spent researching sharkskin to make the slipstream of his suit smaller. The simultaneous feeling of human skin on sandpaper and slick smoothness. Tony hadn't realised he'd caught and held his breath until that moment, and forced himself back into a mostly normal rhythm, reeling, feeling like his skin was suddenly too small for him.

Steve paused, watching him closely, when Tony couldn't find words. "Tony?"

"It's fine," he managed. "New."

Steve blinked. "New?"

"No one else ever..." Tony trailed off. 'Touched me' wasn't quite right, but it wasn't really wrong, either. In the end he stayed silent. Not even Pepper had, beyond a first curious touch or two, those few times she'd been willing to experiment.

When it became clear that Tony wasn't going to continue, Steve stood, and bent at the waist to remove the boxers he'd put on for whatever reason. He'd come in here with the intent to start round two. That much was obvious. Had he thought Tony would say no, or kick him out of the penthouse or something?

Steve dropped the boxers onto the floor and stepped carefully into the water, the contrast in temperature between the water and the air briefly making goosebumps rise on his skin. When he settled on his knees and edged cautiously closer as though Tony would shy away, Tony rolled his eyes. 

"You worry too much," he grumbled and tugged until Steve was plastered against him from chest to 'thigh'.

Steve gave him a startled look when the realisation hit. "I thought you'd have one tail," he asked, looking a little bewildered.

Tony laughed, curling one tail up and around, in a way that would be impossible with human legs, to flop over Steve's shoulder from behind. "Don't believe everything you read, Cap. They're called 'myths' for a reason; they don't get nearly everything right."

Steve turned his head to stare at it blankly, as if he had no idea where it had come from, then his eyes traced the scales down the curve of the limb and into the water of the bath. "Well," he said after a moment, "that's mildly unsettling."

"Changed your mind," Tony taunted him.

"Hardly. Just need to wrap my head around this properly. What else can you do?"

With a shrug, Tony let his hands drift up Steve's torso to rest against the fronts of his shoulders. The soft warm skin under his palms was grounding, and the touch sent some small shivers through Steve that he would never have noticed unless his hands had been there. "Don't know. This is as new to me as it is to you."

"At least," Steve mused as his right hand curled around Tony's cock, "you've still got this. This much is familiar."

"Oh, sure," Tony shot back as the touch made him arch against Steve, "stick to the familiar, why don't you."

"Don't you worry," Steve smirked, apparently having gotten back his mental equilibrium, "I'll get to the new territory."

\------------------------  
Footnotes

[1] For those of you who want more information, I offer Wikipedia links on [the Gulf War](https://en.wikipedia.org/wiki/Gulf_War) and a list of [US military engagements](https://en.wikipedia.org/wiki/Timeline_of_United_States_military_operations#1980.E2.80.931989) in the time period leading up to the Gulf War. Just for context. This isn't strictly required reading for the fic itself.

[2] I'm using [this illustration by Valdes (from the 1920s)](https://s-media-cache-ak0.pinimg.com/736x/df/34/12/df341229fb04a9d4892fb1e76ed0e5bd.jpg) as a visual reference, for this. Mostly because of the way that this fic is set up. In this verse, where merfolk can hide their scales and fins at will to look human, it doesn't really make sense to use the mythos where merfolk only have a single tail, since that would require one hell of a skeletal transformation. In this verse, the two tails have several more joints than human legs do, to give them more flexibility, but they don't flat-out become like vertebrae. They're more like much larger fingerbones with ball-and-socket joints in between them for flexibility.


End file.
